1. Technical Field
The present invention relates to a method for preparing a zinc-histidine self-assembly biomimetic complex that activates a reaction to convert carbon dioxide into a bicarbonate ion, a zinc-histidine self-assembly biomimetic complex obtained by the preparation method, and a method for reducing carbon dioxide using the zinc-histidine self-assembly biomimetic complex.
2. Description of the Related Art
The energy we use is mostly obtained from the heat generated from the combustion of fossil fuels (e.g., petroleum, charcoal, natural gas, etc.) composed of hydrocarbons, but it cannot be acquired without emission of carbon dioxide. Carbon dioxide is a principal component constituting greenhouse gases and accounts for the greatest part of the greenhouse gas emissions.
The climate change caused by the greenhouse gases alters the natural environments of the Earth to raise the global sea level and unusual weather phenomena, such as local downpour, heavy snowstorm, and so forth, causing changes in the terrestrial and marine ecosystems. A bond of sympathy that the concentration of carbon dioxide in air among the gases of which the emission is controllable needs to be reduced to prevent the global warming is developing worldwide and a discussion about the method for reducing carbon dioxide is in progress.
In particular, according to the Kyoto Protocol created in Kyoto, Japan in 1997, the annexed agreement of the U.N. Convention on Climate Change (signed in 1992) specifies a code of conduct such as reduction of greenhouse gas emission aiming at easing the global warming. The Republic of Korea classified in the category of developing countries is exempt from the Kyoto Protocol, which requires nations to reduce their greenhouse gas emissions. But, it is expected that the demand for the reduction of greenhouse gas emissions is increasing in consideration of the tendency towards strengthening the related regulations as a result of the increase in the CO2 emission in Korea and abroad and the current situation that Korea is one of the OECD-member countries emitting a lot of greenhouse gases.
The EU launched the EU emissions trading system (EU-ETS) of allowances for emitting carbon dioxide (CO2) among the companies on Jan. 1, 2005 and began the second trading period among the countries in 2008. The EU-ETS set an upper limit on the total volume of CO2 emissions for 13,000 installations having a generating unit of 20,000 Kw or above in the EU-zone and gave the individual power stations or industrial plants a permit to trade a surplus or shortage of the allowance according to their CO2 emissions. The price of the emission allowance was around 7 to 8 euros per ton of CO2 emissions and tended to rise as the due date for the target reduction of the CO2 emission got closer. A failure to lower emissions resulted in a fine of 40 euros per ton of CO2 emissions, and the fine was increased to 100 euros per ton of CO2 emissions since 2008. The total quantity of the emission allowances to be traded in the EU emission market is estimated at approximately 2.1 billion tons a year, that is, a 10 billion euro a year business. It is expected that the company's purchasing cost for the CO2 emission is going to soar in the future.
With such nationwide institutional demands and change, many studies on the CO2 capture and conversion have been made. As for the CO2 conversion, a variety of chemical conversion methods including inorganic catalysts are being developed and studies on the CO2 capture and conversion using bio-proteins existent in nature are also actively in progress.
The advantage of the CO2 conversion method using proteins and enzymes over the other methods using a catalyst based on inorganic substances is that the reaction takes place at ambient temperature and pressure. A representative example of the enzymes widely used for the CO2 capture is carbonic anhydrase (hereinafter, referred to as “CA”), which CA can convert carbon dioxide into a bicarbonate ion.
In general, the conversion reaction from carbon dioxide to a bicarbonate ion is a kinetically very slow reaction. But, it is known that the organisms including mollusks that synthesize calcium carbonate can use the CA to accelerate the rate of such a reaction. The CA is also known to play a role in the physiological functions, such as respiration, ion transfer, acid-base control, etc. Therefore, the studies on the CO2 capture using the CA are now in the spotlight.
Particularly, the activated site of the CA to convert CO2 has a structure that three histidines surround the Zn ion at the center. The strength of the CA enzyme is that it can react with 104 to 106 CO2 molecules per second in water and rapidly convert the CO2 molecules into HCO3−.
Disadvantageously, however, the conventional carbonic anhydrase (CA) commercially available has a limitation in its large-scale production due to the difficulty in the duplication and purification process, involves high production cost and displays poor thermal stability, which is characteristic to enzymes. Thus there is an urgent demand for developing a substance as a substitute for the conventional CA.